I. Field of the Invention
This invention relates to copiers and, more particularly, to a method and apparatus for monitoring and adjusting various components of electrophotographic copiers to improve their synchronous operation.
II. Background of the Invention
In the process of electrophotography, a cylindrical drum is formed with a photoreceptor surface. The surface is sequentially rotated past a plurality of electrophotographic processing stations whereby the image on an original document may be reproduced onto a copy sheet. In the normal mode of carrying out the process, the photoconductor surface is uniformly charged and then exposed to light rays imaged from the original document to dissipate the charge in areas corresponding to the non-image areas and to allow the charge to remain in the image areas. A latent electrostatic image is thus formed on the photoreceptor corresponding to the image on the original document. Prior to development of the latent electrostatic image, portions of the photoreceptor between electrostatic images are subjected to light from an electroluminescent panel to dissipate the charge on these light-struck portions of the photoreceptor to preclude unnecessary development. The latent electrostatic image is then passed through a development station where dark toner particles, electrostatically charged opposite from the charge of the electrostatic image, are brought into contact with the electrostatic image for its development. The developed image on the photoreceptor surface then moves past a transfer station whereat a sheet of copy paper is fed synchronously into contact with the developed image of the drum. At the transfer station, the toner image is electrostatically transferred from the photoreceptor to the copy sheet. The copy paper is then moved through a fusing device to permanently affix the toner image thereto for the creation of the permanent image. The photoreceptive surface is then cleaned as it passes to the charging station and other subsequent processing stations to complete a cycle of operation and begin a new cycle.
As can be understood, the synchronization of the various electrophotographic processing steps is vital to the creation of a high quality reproduction of the original document. It is equally vital that the copy sheet and the photoreceptor are fed in synchronism with the leading edge of the paper in exact registration with the leading edge of the electrostatic image, that the optical assembly is adjusted to project the optical image from the leading edge to the trailing end of the original document, and that the document conveyor transports the original document onto the document glass of the copier at the correct location. If the copier is adjusted improperly so that one or more of these occurrences is not synchronously effected, a full one-to-one copy of the entire original document cannot be achieved.
Various prior patents disclose methods and apparatus intended to achieve adjustments of the same copier components as those to be adjusted by the present invention. For example, U.S. Pat. No. 4,310,236 to Connin relates to feeding copy sheets to an electrophotographic web so that the copy sheets can be positioned to compensate for positional deviations of the document images from the normal or expected image position. The copy sheet can be adjusted to deliberately provide skew in the copy sheet. There is no provision, however, for adjusting the side edge of the copy sheet. In the preferred embodiment, sensors in the document feeder determine if the document has not been properly positioned on the document glass. This patent, therefore, does not relate to adjustments at initial machine setup but rather to in-process alteration of copy sheet feeding in accordance with document positioning on the document glass.
A technique for mating the leading edge of the copy sheet with the leading edge of the electrostatic image is disclosed in U.S. Pat. No. 4,203,663 to Ogura et al. Like the previously discussed patent, this disclosure is not applicable to adjustments at initial machine setup.
In U.S. Pat. No. 4,272,187 to Birdsall et al, a manufacturing process is disclosed for aligning optical elements within a copier machine through the use of a vidissector camera. This disclosure relates to a manufacturing process and is not pertinent to adjustments at initial machine setup.
Lastly, U.S. Pat. No. 4,243,316 to Gustafson relates to a registration mechanism for a master document on the document glass. Here, once again, the disclosure is not applicable to adjustments at initial machine setup.
As illustrated by the great number of prior patents, efforts are continuously being made in an attempt to accurately and conveniently create a complete and exact copy of an original document automatically through a proper timing sequence of components of the copier. Nothing in the prior art discloses or suggests the present inventive combination of method steps and apparatus for completely and exactly creating copies of original documents through various adjustments to effect the precisely synchronized operation of certain critical components of the copier.
The present invention achieves its purposes, objectives, and advantages over the prior art through a new, useful, and unobvious combination of components for synchronously conveying an original document to the document glass, the projecting of the image of the original document to the photoreceptor, and feeding of the copy sheet to the electrostatic image in a convenient and repeatable manner. All of this is accomplished with a minimum number of functioning parts, at a minimum of cost, and through the utilization of only readily available materials and conventional components.
These objectives and advantages should be construed as merely illustrative of some of the more prominent features and applications of the present invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and advantages as well as a fuller understanding of the invention may be had by referring to the summary of the invention and detailed description describing the preferred embodiments of the invention in addition to the scope of the invention as defined by the claims taken in conjunction with the accompanying drawings.